It is attempted to develop flame retardant polyurethane coatings, which have received significant attention in recent years. It is the purpose of this study to synthesize new reactive polyurethane coatings containing halogen. Lactone based modified polyester polyols, using trichlorobenzoic acid as chlorine moiety (TBAOs) were synthesized. These polyesters were cured with isophorone diisocyanate (IPDI)-isocyanurate at room temperature (TBAPUs). Physical properties of these flame retardant coatings were similar with those of non-flame retardant coatings. The flammability of coatings was strongly dependent on the chlorine contents. We found that the increasing chlorine contents showed better flame retarding properties and that, however, they also resulted in more smog generation during combustion. The detailed results of flammability test using various methods indicated 24~26% in LOI and 3.7~5.3 cm char length in 45˚ Meckel burner method.